Structural wood decay

High indoor humidity and resulting

condensation

Expansive soil, which may crack the

foundation of a home through changes in

volume, or softened soil, which may lose its

ability to support an overlying structure

Undermined foundations

Metal corrosion

Ice dams

Mold growth. Mold can only grow in the

presence of high levels of moisture. It can

lead to conditions like: asthma, allergies, lung

disease, and/or compromised immune

systems

Air infiltration: Air naturally moves from high-

pressure areas to lower ones by the easiest

path possible, such as a hole or crack in the

building envelope. Replacement air will

infiltrate through the building envelope unless

unintended air paths are carefully and

permanently sealed

Diffusion through building material: Most

building materials slow moisture diffusion, to

a large degree

Leaks from roof

Plumbing leaks

Flooding

Human activities, including bathing, cooking,

dishwashing and washing clothes.

In the northern U.S., moisture vapor problems

are driven primarily by high indoor relative

humidity levels, combined with low outdoor

temperatures during the winter.

In the southern U.S. (especially the southeast),

the problem is largely driven by high outdoor

humidity and low indoor temperatures during

summer months.

Mixed climates are exposed to both

conditions and can experience both types of

problems.

Humid climates, in general, will be more of a

problem than dry climates. Wind-driven rain is

the main cause of leaks through the building

envelope.

Roof penetrations increase the likelihood of

water leaks due to failed gaskets, sealants and

flashing. The number of roof penetrations may

be reduced by a variety of technologies and

strategies, including:

Consolidation of vent stacks below the roof;

exhaust fan caps routed through walls instead

of the roof

High-efficiency combustion appliances, which

can be sidewall-vented

Electrically powered HVAC equipment and

hot water heaters that do not require flue; and

Adequate flashing. Oftentimes, inspectors

discover missing, incorrectly installed or

corroded flashing pipes

Distribution pipes and plumbing fixtures can

be the source of large amounts of moisture

intrusion

A non-functioning exhaust fan overloads the

bathroom with damp air. If the exhaust fan

doesn’t turn on automatically when the

bathroom is in use, consider switching the

wiring or switch

The bathroom sink is a common source of

moisture intrusion and damage

Bathroom windows need to perform in a wide

range of temperature conditions

If some water remains in the bathtub after

draining, it may be a warning sign of possible

structural weakening and settlement in the

floor beneath the tub

The water heater tank should be clean and

rust-free

The area around the water softener tank

should be clean and dry

Check that all through-the-wall penetrations

for fuel lines, ducts, and electrical systems of

heating system are well-sealed. All ducts

should be clean and dust-free. Inspect the air

supply registers in the house for dust

accumulation

Filters, supply lines, exterior wall penetrations,

vents, ductwork and drainage of the cooling

system must all be in good working order to

avoid moisture problems

Look for stains or discolorations at all roof

penetrations. Chimneys, plumbing vents and

skylight wells are common places where

moisture may pass through the roof.

Are there areas of the insulation that appear

unusually thin?

Rust or corrosion around recessed lights are

signs of a potential electrical hazard.

Model building codes typically require damp-

proofing of foundation walls. The damp-

proofing shall be applied from the top of the

footing to the finished grade. Parging of

foundation walls should be damp-proofed in

one of the following ways:

Bituminous coating

3 pounds per square yard of acrylic modified

cement;

1/8-inch coat of surface-bonding cement

Any material permitted for water-proofing

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